1. Field of the Invention
This invention relates generally to systems and apparatus for extraction and utilization of bleed air from the compressor section of a gas turbine engine, and relates more particularly to such systems and apparatus for supplying pressurized breathing air to the passenger cabin of an aircraft propelled by gas turbine means.
2. Prior Art Problem
If any oil leaks into a source of bleed air within a gas turbine engine, the aircraft cabin ventilated by that air may smell and appear smoky, an annoyance to the cabin occupants. Moreover, such oil-contaminated air can not only foul plastic surfaces and windows but can also seriously interfere with the proper operation of air-conditioning components such as air bearings of turbo-expanders. It is very difficult to prevent small amounts of oil from leaking into the compressor stage, as from a bearing. One remedy for this problem is to place a charcoal filter in the ventilating air duct. However, that filter tends to be bulky and to introduce a considerable pressure drop; moreover, the charcoal must be replaced when it becomes contaminated with oil.